A typical air cargo net, also called pallet net or air freight net, is cruciform in shape, and has a generally rectangular central part of about the same size as the pallet, and four generally rectangular lobes or wings extending there from, having a length about equal to the maximum load height of the pallet. To secure cargo on a pallet, the net is placed over the cargo and the net lobes are brought down. The ends of the lobes are attached to the sides of a pallet with the pallet attachment fittings, e.g. so-called double studs, fixed to a border rope forming the peripheral end meshes of a lobe, which fittings are adapted to engage with complementary devices on the pallet. Adjacent sides of the lobes meeting at the corner are releasable secured together, for example with a corner rope or lashing line, which extends from the central panel between the lobes, or with connecting elements attached to the sides of the lobes. The air cargo net can further comprise a plurality of adjusting hooks, for example reefing or spring-closed hooks, fixed to a rope of a mesh, which can be used to further tension the net over the cargo by pulling and connecting to other mesh ropes. To release the net for unloading, above actions are reversed.
Air cargo nets should fulfil different requirements in order to safely and securely restrain cargo loads from shifting on a pallet during loading and unloading, and during flight; also under more extreme circumstances like during atmospheric turbulence. An air cargo net should thus be strong, and resistant to abrasive conditions, but at the same time be as lightweight as possible, in order not to unduly increase the payload of an aircraft. During use, cargo nets are subjected to substantial wear and tear conditions leading to extensive abrasion on the net, or damage from repeated attachment and removal from the cargo pallet, or from dragging across floors.
Air cargo nets should fulfil various design and performance criteria, as described in various standards, like NAS 3610. Checking the condition of a net before each use is also prescribed, and a pallet net shall be deemed inoperative if it exhibits a defect like more than one strand of frayed or otherwise damaged rope, or missing or inoperative attachment fittings (see e.g. SAE ARP5486).
Such an air cargo net is for example known from WO 2004/082995 A1. This publication discloses an air cargo net comprising a plurality of ropes made from polymer fibres, which ropes are joined at intervals to form meshes, the net having a rectangular central part and four rectangular lobes projecting there from, the peripheral meshes of each lobe being formed by a border rope, each border rope having a plurality of attachment fittings, and four corner ropes extending from the central panel between the lobes. The net and border ropes are preferably braided from ultra-high molar mass polyethylene fibres, whereas the corner ropes preferably are braids from polyester, polyamide or polypropylene fibres. Attachment fittings and adjusting hooks are fixed to the net by the respective border and net ropes passing through an eye of the fitting or hook. This way of connecting fittings is representative for state-of-the art cargo nets.
A drawback of the known air cargo nets is that the operation of releasing the net from the cargo for unloading is frequently troublesome, due to one or more of the attachment fittings not readily unlocking; for example caused by corrosion or pallet edge damage. It appears quite common for cargo handlers in such case to cut the border rope with a knife or scissors at the mesh with the connected malfunctioning fitting. Such a borderline cut necessitates net repair, which is costly for at least two reasons. Firstly, a repair event withdraws the net from use in air cargo transport until repair is finished; requiring the airlines to keep additional net stock to bridge repair times. Secondly, net repair itself may only be performed by certified companies, and is laborious.
The object of the invention is therefore to provide an air cargo net that is less prone to cutting of the border rope, and that has longer effective service time.
This object is achieved according to the invention with an air cargo net wherein the attachment fittings are connected to the border rope by replaceable connecting ropes.
The connecting rope is an auxiliary rope that is replaceably attached to the net rope and fitting, for example by knotting. Replaceable is understood to mean that the connecting rope can be removed from the net without damaging other net ropes, for example by untying the knot that attaches the connecting rope to the net, by simply cutting the connecting rope, and a replacement connecting rope with fitting can be subsequently attached. The connecting rope has such strength that after being attached to the border rope and fitting the net still fulfils all relevant requirements.
A cargo net wherein the attachment fittings are connected to the border rope by a replaceable connecting rope needs less frequent repair off-site. The cargo handler, for example, can cut or remove the connecting rope to release the net from the pallet, instead of cutting the net or border rope. A further advantage of the replaceable connecting rope is that any person, but preferably a qualified technician, can locally and quickly replace a missing or damaged connecting rope and fitting, such that the cargo net is directly operational again for a next flight. Since the net and border ropes forming meshes are not damaged the net itself needs not be repaired at specialised companies. This way the number of repair events and the number of spare nets of an airline are significantly reduced, the use efficiency of the net is increased; and overall system costs are markedly reduced.